From 2-spyware.com
From themes to extensions – users love to customize their web browser, be it Google Chrome, Mozilla Firefox, MS Edge, or Safari. Browser extensions are something that is particularly useful when trying to implement new features or make the existing ones more appealing. They can also be used for security measures, as they can detect and warn users about malicious websites that use phishing or include malicious code.
Besides all the goodies, malicious add-ons also exist, even though they are not very prevalent. For example, people might download a fake version of a very reputable app or install it along with other software. These extensions are commonly detected and removed by security software so, as long as users use them, they are relatively safe from those.